JPH03260322A - Exhaust port variable device of two cycle engine - Google Patents

Abstract

PURPOSE:To improve strength and durability by extending a reinforcing wall which devides an exhaust port into left and right to a radial direction outer side of a cylinder bore, to the position to divide a wall face of a support member which a part of the upper part of an exhaust port, and increasing a sectional area of the reinforcing wall. CONSTITUTION:At an inner wall of a cylinder bore 5a formed at a cylinder block 5, an exhaust port 35 opened and closed by a piston 33 is opened. At the exhaust port 35, a control valve 36 which variable controls the port opening area and a reinforcing wall 48 which divides the inner part into left and right area arranged. In this device, a through hole 45 which opens to the upper part of the exhaust port 35 is formed, and the support member 46 of the control valve 36 is formed at the inner part of the inner part of the through hole 45. One of the upper wall part of the exhaust port 35 is formed of a wall face 46a of the support member 46, the outer end of the reinforcing wall 48 is extended toward the radial direction, and both the up- and down-ends of the reinforcing wall 48 is connected to the cylinder block 5 with the upper face of the through holes 45 and the lower face of the exhaust port 35.

Description

Detailed Description of the Invention A1 Object of the Invention (1) Industrial Application Field The present invention has an exhaust port opened and closed on the inner wall of a cylinder bore formed in a cylinder block, which is opened and closed by a piston that reciprocates within the cylinder. A variable exhaust port for a two-stroke engine, wherein the exhaust port is provided with a control valve that variably controls the opening area of the exhaust port, and a reinforcing wall that extends in the radial direction of the cylinder bore and divides the exhaust port into left and right halves. Regarding equipment.

(2) Prior Art The exhaust port variable device for the two-stroke engine described above is already known, as described, for example, in Japanese Patent Application Laid-Open No. 192913/1983. According to such an exhaust port variable device, it is possible to reduce the opening area of the exhaust port to prevent fresh air from blowing through when the engine is in a low speed operating range including idling, and it is possible to prevent fresh air from blowing through when the engine is in a low speed operating range including idling. If possible, it will be possible to increase the opening area of the exhaust port and improve the output.

(3) Problems to be Solved by the Invention However, in the conventional exhaust port variable device described above, the width in the cylinder bore radial direction of the reinforcing wall provided at the exhaust port to reinforce the vicinity of the exhaust boat formed in the cylinder block is small. However, heat transfer from the reinforcing wall heated by the exhaust gas passing through the exhaust port to the cylinder block is insufficient, resulting in a disadvantage that the supporting strength and durability of the reinforcing wall are reduced. Therefore, it is necessary to increase the thickness of the reinforcing wall, which increases exhaust resistance and reduces engine output.

The present invention has been made in view of the above-mentioned circumstances, and improves heat conduction from a reinforcing wall provided in a variable exhaust port device of a two-stroke engine to a cylinder block, thereby increasing its strength and durability, and improving the exhaust port of a two-stroke engine. The purpose is to reduce resistance.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides an exhaust port that is opened and closed on the inner wall of a cylinder bore formed in a cylinder block by a piston that reciprocates within the cylinder bore. is opened, and the exhaust port is provided with a control valve that variably controls the opening area of the exhaust port, and a reinforcing wall that extends in the radial direction of the cylinder bore and partitions the exhaust port into left and right sides.
In the exhaust port variable device for a cycle engine, a through hole that opens at the upper part of the exhaust port is formed in the cylinder block wall in the radial direction of the cylinder bore, and a support member that supports the control valve is installed in the through hole, A wall surface provided on the supporting member forms a part of the soil wall of the exhaust port, and an outer end of the reinforcing wall extends radially outward of the cylinder bore at least to a position where the wall surface of the supporting member is divided into left and right sides. Further, the lower end and the upper end of the reinforcing wall are connected to the cylinder block at the lower surface of the exhaust boat and the upper surface of the through hole, respectively.

Here, "upper" and "lower" are defined as referring to the combustion chamber side and crankcase side of the cylinder block, respectively, regardless of the arrangement direction of the cylinder block.

(2) Effect According to the above-mentioned feature, when the reinforcing wall that partitions the exhaust port into left and right sides is heated by the exhaust gas passing through the exhaust port, the heat is transferred to the lower surface of the exhaust port to which the lower end of the reinforcing wall is connected. , the upper end of the reinforcing wall is released into the cylinder block from the upper surface of the through hole of the supporting member to which it is connected. At this time, since the reinforcing wall extends outward in the radial direction of the cylinder bore to a position where the wall surface of the support member forming a part of the earthen wall of the exhaust boat is divided into left and right, the width of this reinforcing wall is set in the radial direction of the cylinder bore. This makes it possible to secure a sufficiently large area. This increases the cross-sectional area of the reinforcing wall, improving heat removal, increasing its strength and durability, and making it possible to reduce the thickness of the reinforcing wall to reduce exhaust resistance.

(3) Examples Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is an overall side view of a motorcycle equipped with an engine E equipped with an exhaust boat variable device according to an embodiment of the present invention. A front wheel Wf is pivoted on the lower end of the front fork 2 which is supported by the front part of the vehicle body frame F and can be rotated from side to side by a handle l, and a rear fork 3 is supported at the rear of the front fork 2 so as to be swingable up and down. A rear wheel Wr connected to and driven by the engine E is mounted on a shaft at the rear end of the vehicle. The engine E is a single-cylinder two-stroke engine, and as is clear from FIG. 6 is approximately 36 along the front surface of the crankcase 4 located below.
After being bent by 0°, a muffler 7 extends rearward through the right side of the cylinder block 5 and is provided at the rear end of the vehicle body frame F.
is connected to.

FIG. 3 is a horizontal cross-sectional view of the crankcase 4, showing a control valve drive mechanism 8 for driving a control valve, which will be described later, provided in the exhaust boat of the engine E. The control valve drive mechanism 8 is housed in a storage section 4a that is integrally connected to the front right side of the crankcase 4 of the engine E, and a crankshaft 11 supported by the crankcase 4 via a pair of ball bearings 9 and 10. A governor 13 is provided which is interlocked with a water pump 12 for circulating cooling water, which is driven by a water pump 12 for circulating cooling water. The governor 13 is a bowl that is fixed to a pump shaft 16 supported in a storage R4a via a pair of ball bearings 14.15, and has a ring gear 18a on its outer periphery that meshes with an output gear 17 fixed to the end of the crankshaft 11. a lamp plate 18 having a shape, a slide plate 19 slidably supported on the pump shaft 16 so as to face the recess of the lamp plate 18, and a slide plate 19 disposed between the lamp plate 18 and the slide plate 19 so as to be freely movable in the radial direction. It is composed of a centrifugal weight 20 provided therein. An intermediate portion of a lever 23 is pivotally supported on a bin 21 installed inside the storage portion 4a, and a fork portion 23a formed at one end of this lever 23 is in contact with a pressing surface 19a of the slide plate 19. . A slide member 26 biased by a spring 25 is slidably engaged with a guide groove 24 formed parallel to the pump shaft 16 with the pin 21 in between, and the stepped portion 2
6a, a fork portion 23 formed at the other end of the lever 23;
b is in contact. An arm 28 provided at the lower end of a drive shaft 27 rising from the housing portion 4a of the crankcase 4 toward the cylinder block 5 is engaged with a shaft portion 26b formed at the end of the slide member 26. Therefore, engine E
As the rotational speed of the crankshaft 11 gradually increases, the centrifugal weight 20 of the governor 13
The slide plate 19 moves radially outward along the
Press to the left in the figure. As a result, the lever 23 swings clockwise, presses the slide member 26 to the right against the spring 25, and rotates the drive shaft 27, which engages the shaft portion 26b via the arm 28, by a predetermined angle. let

As shown in FIGS. 4 to 6, a transmission mechanism 29 that transmits the driving force of the control valve drive mechanism 8, that is, the rotation of the drive shaft 27 to the control valve described later, is connected to the upper part of the crankcase 4. A horizontal shaft 30 is arranged horizontally at the front lower part of the cylinder block 5, and a vertical shaft 3 is connected to the left end of the horizontal shaft 30 and stands up vertically on the left side of the cylinder block 5.
1 (see Figure 6). An eccentric pin 32 provided at the upper end of the drive shaft 27 is engaged with a groove 30a formed at the right end of the horizontal shaft 30, and as the drive shaft 29 rotates, the horizontal shaft 30 is moved through the eccentric pin 32. Moves back and forth from side to side. A rack 30 formed at the left end of this horizontal shaft 30
b is a pinion 31a formed at the lower end of the vertical shaft 31;
are in mesh with each other, so that the movement of the horizontal shaft 30 that reciprocates left and right becomes a reciprocating rotational motion and is transmitted to the vertical shaft 31.

As shown in FIGS. 7 to 10, a cylinder bore 5a into which a piston 33 slides is formed inside the cylinder block 5, and a plurality of scavenging boats 34 and one exhaust port 35 are opened on the inner surface of the cylinder bore 5a. There is. A control valve 36 is attached to the exhaust port 35 so as to be vertically movable in order to variably control the height of its upper edge. A sleeve 40 to which a driving force is transmitted via a torsion spring 38 and an interlocking plate 39 of a lost motion mechanism 37 that absorbs excessive rotation of the vertical shaft 31 is fitted into the upper end of the vertical shaft 31. A worm gear 40a provided on this sleeve 40 meshes with a worm wheel 43a provided at one end of a pivot 43 disposed in parallel to the horizontal shaft 30 through a pair of ball bearings 41, 42 at the upper part of the cylinder block 5, This axis 43
A bifurcated arm 44a of an arm member 44 fixedly engaged with the control valve 36. The transmission mechanism 29, ie, the horizontal shaft 30 and the vertical shaft 31, are shown in FIGS. 7 and 8.
As is clear from the figure, it is disposed along the dead space formed between the pivot 42 of the arm member 44 that drives the control valve 36 and the cylinder bore 5a, and due to the above-described layout of the transmission mechanism 29, the engine E Efforts have been made to reduce the size. Further, the transmission mechanism 29 and the lost motion mechanism 37 are covered by a removable cover 5b provided on the left side of the cylinder block 5, that is, on the opposite side to the exhaust pipe 6 disposed along the right side of the vehicle body.
It is designed so that maintenance can be performed without removing the exhaust pipe 6.

Next, the structure of the control valve 36 will be explained in detail with reference to FIG. 11. At the front of the cylinder block 5, an exhaust port 35 that opens into the inner surface of the cylinder bore 5a is formed diagonally downward toward the front. is formed in the radial direction of the cylinder bore 5a. Inside the through hole 45, the control valve 36, the pivot 42,
A support member 46 that supports the arm member 44 is inserted from the outside as a unit and fixed to the cylinder block 5 with bolts 47. An inclined wall surface 46a is formed at the lower end of the support member 46, and when the support member 46 is inserted into the through hole 45, the wall surface 46a constitutes a part of the earthen wall of the exhaust port 35. . As is clear from FIGS. 8 and 10, the inside of the exhaust port 35 has a vertical reinforcing wall 48 extending in the radial direction of the cylinder bore 5a.
It is divided into two parts, left and right. The lower end of the reinforcing wall 48 is connected to the cylinder block 5 at the lower surface 35a of the exhaust port 35.
and its upper end is connected to the upper surface 45 of the through hole 45.
It is connected to the cylinder block 5 at point a. The upper part of the reinforcing wall 48 is fitted into a slot 7) 46b formed vertically in the support member 46 inside the through hole 45.

The control valve 36 consists of two members, a right valve body 36r and a left valve body 361, which are formed symmetrically with respect to the reinforcing wall 48, and both valve bodies 36r and 361 have their guide portions 36a formed in the support member 46. It is engaged with the guide groove 46c and supported so as to be freely movable up and down. Each valve body 36r, 36J includes an arcuate valve portion 36b that smoothly connects to the cylinder pore 5a and slides on the piston 33, and this valve B56b and the guide portion 36a are integrally connected via a connecting portion 36c. . A sealing surface 36b formed on the back surface of the valve portion 36b.
z and a sealing surface 46d formed at the tip of the support member 46 are in sliding contact with each other, and both valve bodies 36.

Airtightness is ensured when 361 slides up and down with respect to the support member 46. Further, the tip of the arm 44a of the arm member 44 is inserted into the hole 36a1 formed in the guide portion 36a, and the movement of the arm member 44 causes both the valve bodies 36r,
361.

The fully open position where both the valve bodies 36r and 361 are raised the most is the step i formed in the valve portion 36b of the valve bodies 36r and 361.
36b2 is regulated by abutting against a stepped portion 46e formed on the support member 46, and the fully closed position in which both the valve bodies 36r and 361 are lowered the most is reached by a stopper 44c protruding from the boss portion 44b of the arm member 44. It is regulated by contacting bolt 4g.

Next, the operation of the embodiment of the present invention having the above-described configuration will be explained.

When the engine E is currently in a low speed operating range including idling, as shown in FIG.
Both valve bodies 36r, 36j!
The guide portion 36a is inserted into the guide groove 46c of the support member 46.
is guided to the fully open position shown by the solid line. In this state, the opening period of the exhaust boat 35 becomes the shortest, reducing the blow-through of fresh air introduced into the cylinder bore 5a from the scavenging boat 34 to the exhaust port 35, and suppressing the increase in harmful compounds in the exhaust gas.

During the process in which the rotational speed of the engine E passes through the medium-speed operating range and reaches the high-speed operating range, as shown in FIG. Lever 23, shaft portion 26b1 of slide member 26, drive shaft 27, horizontal shaft 30, and vertical shaft 31
each move and rotate in the direction of the arrow, and the arm member 44 is connected to the upper end of the vertical shaft 31 via a pivot 43 connected to the upper end of the vertical shaft 31.
swings upward. As a result, the control valve 36 rises to the fully open position shown by the chain line in FIG. 9, and both valve bodies 36 open.

36I! The lower surface of the exhaust port 35 is flush with the wall surface 46a of the support member 46 that constitutes the upper surface of the exhaust port 35, and the effective opening area of the exhaust port 35 is maximized. As a result, a large amount of exhaust gas generated in the medium and high speed rotation range of the engine E is efficiently discharged to the exhaust port 35, and output can be increased by improving exhaust efficiency. In addition, after the control valve 36 reaches the fully open position while the engine E moves from the medium-speed operating range to the high-speed operating range, the vertical shaft 31 of the transmission mechanism 29 connected to the control valve drive mechanism 8 rotates excessively. However, the rotation is absorbed by the lost motion mechanism 37 and is not transmitted to the control valve 36.

When high-temperature exhaust gas passes through the exhaust port 35 due to the operation of the engine E, the reinforcing wall 48 that partitions the exhaust port 35 into left and right sides is heated by the exhaust gas, and the heat is transferred to the exhaust port 35 to which the lower end of the reinforcing wall 48 is connected. A lower surface 35a;
It escapes into the cylinder block 5 from the upper surface 45a of the through hole 45 to which the upper end is connected. At this time, since the outer end of the reinforcing wall 48 in the radial direction of the cylinder bore 5a extends to the outside beyond the outer edge of the wall surface 46a formed on the lower surface of the supporting member 46 (the reinforcing wall 48 in FIG.
(See the sleeve) 46b of the support member 46 into which the reinforcing wall 48 fits in the figure, and the cylinder bore 5 of the reinforcing wall 48.
a An extremely large width in the radial direction is ensured. Thereby, heat is efficiently transferred from the reinforcing wall 48 to the cylinder block 5, and the strength and durability of the reinforcing wall 48 are improved.

Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the embodiments described above, and various small design changes may be made without departing from the scope of the invention described in the claims. It is possible to do so.

For example, in the embodiment, a case where the present invention is applied to an upright two-stroke engine has been described, but it is obvious that the present invention can also be applied to other types of engines such as a horizontal two-stroke engine.

C1 Effects of the Invention As described above, according to the present invention, the radius of the cylinder bore is increased to the point where the reinforcing wall that partitions the exhaust port into left and right sides divides the wall surface of the support member that forms part of the soil wall of the exhaust port into left and right sides. Since the reinforcing wall extends outward in the radial direction of the cylinder bore, it is possible to ensure a sufficiently large width of the reinforcing wall in the radial direction of the cylinder bore. As a result, the cross-sectional area of the reinforcing wall increases, and heat conduction from the reinforcing wall heated by exhaust gas to the cylinder block becomes better, and its strength and durability can be increased. In addition, due to the increased stiffness of the reinforcing wall, it is possible to maintain the necessary strength even if the thickness of the reinforcing wall is reduced, resulting in reduced exhaust resistance in the exhaust boat and improved engine output. can contribute.

[Brief explanation of drawings]

FIG. 1 is an overall side view of a motorcycle equipped with an engine equipped with an exhaust boat variable device according to an embodiment of the present invention, and FIG. 2 is a view taken along the line ■-■ in FIG. ■- in Figure 1
■A cross-sectional view of the crankcase taken along lines, Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3, and Figure 5 is a cross-sectional view taken along line 4I! Figure 6 is a perspective view showing the driving force transmission path from the control valve drive mechanism to the transmission mechanism, and Figure 7 is a partial vertical cross-section of the cylinder block taken along line ■-■ in Figure 8. 8 is a cross-sectional view of the cylinder block taken along the line ■-■ in FIG. FIG. 11 is a vertical cross-sectional view of the cylinder block taken along the line X-X, and is an exploded perspective view of the control valve and its surroundings. 5... Cylinder block, 5a1 cylinder bore, 33
...Piston, 35...Exhaust port, 36...Control valve, 45...Through hole, 46...-Support member, 46a
...Wall surface, 48...Reinforcement wall

Claims (1)

[Claims] The cylinder bore (5) formed in the cylinder block (5)
an exhaust port (35) opened and closed by a piston (33) reciprocating within the cylinder bore (5a) on the inner wall of the cylinder a);
is opened, and the exhaust port (35) is connected to the exhaust port (35).
35), and a reinforcing wall (48) that extends in the radial direction of the cylinder bore (5a) and partitions the exhaust port (35) into left and right sides. In the exhaust port variable device, a through hole (45) opens at the upper part of the exhaust port (35).
) to the cylinder block (5) wall and the cylinder bore (5a)
A support member (46) that supports the control valve (36) is installed in the through hole (45), and a wall surface (46a) provided on the support member (46) is used to conduct the exhaust gas. It forms part of the upper wall of the port (35) and the reinforcing wall (4)
8) at least the outer end of the support member (46) (
Cylinder bore (5a) to the position where it is divided into left and right parts.
) and its reinforcing wall (4
8) A variable exhaust port device for a two-stroke engine, characterized in that the lower end and the upper end are connected to the cylinder block (5) at the lower surface of the exhaust port (35) and the upper surface of the through hole (45), respectively.